1. Technical Field
This invention generally relates to structures used to support offshore components. In particular, this invention relates to support structures for, for example, offshore wind turbines, or the like.
2. Description of the Related Art
Conventional offshore support structures have deck legs that are vertical or are battered outward as they extend downwards. Various conventional arrangements provide sufficient structurally support for the deck and offshore device but the associated dimensions of structures result in high material and installation expense. Wind turbines have traditionally been supported on mono-piles when placed offshore. However, recently, efforts include positioning wind turbines in deeper water (approximately six to seven or more miles offshore) in part to increase the aesthetics of the view from the shoreline. However, with the movement of wind turbines further offshore, the employment of mono-piles as the base on which wind turbines are placed has become less cost effective.
Jacket type foundations or support structures with driven pipe piles have been used to support offshore wind turbines in recent years as the offshore wind industry has considered deeper water sites not previously considered feasible for monopile or gravity type foundations based on the added cost. As turbines grew in size to generate more power, the complexity and weight of the transition piece, located between the lower supports and the wind turbine tower, increased. This joint is typically a cast, forged, or heavy wall steel welded connection manufactured during the onshore fabrication phase of construction. The fabrication and installation of heavy wall joints can be a significant cost component to the wind turbine foundation.